It is known that, through legal rules, emergency beacons are installed on aircrafts, so as to allow, in the case of a crash, a detection of the wreck by rescue teams, and the recovery of what is commonly referred to as flight recorders.
These flight recorders are used on aircrafts for recording the main information linked to the flight. Their analysis carried out a posteriori after an incident or an accident should allow determining the causes thereof. There are two types of flight recorders:                a conversation recorder in the cockpit, of the Cockpit Voice Recorder (“CVR”) type, recording ground-board conversations, but also conversations between the crew members in the cockpit; and        a digital flight data recorder, of the Digital Flight Data Recorder (“DFDR”) type, recording flight technical data, such as the trajectory, the altitude, the attitude, the speed, etc.        
The evolution of the technologies and the miniaturization now make it possible to achieve combined (DFDR and CVR) recorders that should result, in a near future, in the associated rules being modified. The number of parameters being recorded depends on the characteristics of the flight recorder. While twenty-eight parameters represent generally the minimum being required, most recent airplanes could be provided with flight recorders able to record up to one thousand three hundred data.
These two flight recorders are generally installed at the rear of the aircraft, in an area being in principle the least exposed one upon an impact with the ground or with a water surface. Moreover, they are designed so as not to be destroyed during an air crash. The recorded data are protected by three layers of materials, intended for ensuring their survival to shocks, to a fire and/or to a deep immersion.
Each flight recorder is additionally provided with a beacon, of the Underwater Locator Beacon (“ULB”) type, automatically triggering upon a crash of the aircraft on a solid or liquid surface and emitting, every second and for a minimum period of time of 30 days, an omnidirectional ultrasound signal at a frequency of 37.5 kHz at 160 dB, so as to aid the localization of the aircraft. This signal is able to be detected as down to a depth of about 6000 meters, via in particular the use of specific passive hydrophones, being towed behind rescue ships deployed on the area of the accident.
However, if the crashed aircraft is submerged in an area where the sea ground is very rough, or if it is deeply burned in a free-flowing ground or even if important metallic elements are present in the area being considered, it is possible that the detection by the rescue teams of the signals emitted by the emergency beacon is extremely difficult, or even nearly impossible. This is a real problem for the air companies, the aircraft manufacturers and still more for the families of the victims of the accident.
The present invention aims at solving these drawbacks. It relates to a device for automatically aiding the localization of a wreck of an aircraft, in particular of a transport airplane, being submerged in a sea water expanse (sea or ocean), including as a result of a crash.